The universal rolling method is generally used in rolling shaped steel having flanges such as H-sections (hereinafter abbreviated as H-sections or others). FIG. 9 shows views of an example of the universal rolling method. Rolling stand (1) represents a breakdown stand which rolls a bloom of cross-section (1-1) into a beam blank of (1-2). Rolling stand (2) indicates a universal rolling stand, in which the beam blank (1-2) is reduced the web thickness by a pair of upper and lower horizontal rolls (2a) and reduced the flange thickness simultaneously by a pair of vertical rolls (2b) and by the horizontal rolls (2a). This universal rolling is repeated several times. (2-1) denotes cross-section of the rolling material in early pass, and (2-2) denotes cross-section of the rolling material after several passes of the universal rolling.
Rolling stand (3) indicates an edging stand. The edging stand (3) is arranged adjacent to the universal rolling stand (2). In the edging stand (3), a pair of upper and lower edging rolls (3a) roll the flange edges of the rolling material so that the edges of the flanges are forged, and the dimension of the flanges is adjusted. The edge rolling is repeated several times between universal rolling passes, e.g. alternately.
That is, rolling material (2-1) is edge rolled into (3-1), and in case of rolling material (2-2), widening the gap of the upper and lower edging rolls (3a), (2-2) is edge rolled into (3-2).
But, in this edging rolls (3a), when the rolling material (3-2), for example, is edged, a clearance (S) occurs between edging roll (3a) and its corresponding part of the web portion of 3-2). Because of this clearance (S), the amount of reduction by the edge rolling is unstable, and since (3-2) may sway right and left, the edging roll cannot guide the section (3-2) correctly. These have resulted in wrong dimensions and shapes of H-sections or others. In FIG. 9, rolling stand (4) represents a universal finishing stand, in which a pair of upper and lower horizontal rolls (4a), and a pair of right and left vertical rolls (4b) finish the shape and dimensions of the section (3-2) into a product (4-2).
FIGS. 10A to FIG. 10B2 are adverse examples which take place in the conventional edge rolling method. FIG. 10A shows an example in which there is a clearance between the edging roll and its corresponding part of the web portion of a rolling material, and a rolling material is deformed. FIG. 10B1 shows an example in which only the upper roll contacts its corresponding part of the web portion, pushing down the web portion. When the web portion is pushed down, as shown in FIG. 10B1, the rolling material results in the so-called web-off-centered H-section as shown in FIG. 10B2 after it is reformed. FIG. 10C shows an example in which the edging rolls are rolling the flange edges guiding with the web portion. The edging rolls of FIG. 10C are effective to prevent the web-off-center of the H-sections. But in this process, in case of changing the edge rolling operation from one section to another section, the edging rolls of a different lc is required. That is, in the rolling mill where many kinds of shaped steel having different flange widths and web thicknesses are rolled, and in the case of FIG. 10C, it is required to have always a large number of rolls having a variety of lc distances and to replace them frequently in accordance with lc of the rolling material. But this operation is very disturbing. Furthermore, in the edge rolling of FIG. 10C, the peripheral speed of the edging roll differs at the flange edges of a rolling material and at the web portion thereof. This causes scabby surfaces of the product and uneven abrasion of the roll.
Japanese Patent Laid-Open Publication No. 077107/1987 and Japanese Patent Laid-Open Publication No. 60008/1988 edging rolls which can be used commonly for a variety of rolling material having different flange widths and web thicknesses, and having a function to roll the flange edges guiding with the web portion. But in this art of using a single eccentric sleeve, as will be described below, the rolling position of the flange edges must be in advance or behind of the guiding position of the web portion. This makes it difficult to obtain a smooth edging operation, and causes upsweep or downsweep of the rolling material and inaccurate sectional dimensions of the product.